# How to find Effective inductance for series/parallel mutually coupled coils

Discussion in 'Homework Help' started by nlr_1986, Aug 20, 2010.

1. ### nlr_1986 Thread Starter New Member

Aug 20, 2010
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Hi to all the members!
i have been given one problem of finding effective induactance for the coils as drawn in figure between ab terminal.
L1=L2=L3=2H and M=1,
so, how i could get the solution.

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2. ### The Electrician AAC Fanatic!

Oct 9, 2007
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Your subject line mentions "mutually" coupled coils, but your schematic doesn't show any mutual coupling. Without knowing the mutual inductance, you can't calculate the answer.

3. ### nlr_1986 Thread Starter New Member

Aug 20, 2010
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I have indicated the dots in figure and mutual iductance M=1 for three coils
and this example is given as unsolved to me and i want to get solution of it

4. ### retched AAC Fanatic!

Dec 5, 2009
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Series inductance and parallel inductance?

Do you want to know the inductance as measured at the dots?

5. ### nlr_1986 Thread Starter New Member

Aug 20, 2010
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i want effective inductance between terminal A&B.

Apr 26, 2005
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7. ### t_n_k AAC Fanatic!

Mar 6, 2009
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Has anyone got a solution for this one. I assumed the OP meant the mutual inductance from any one winding to another was the same value of 1H.

After some laborious algebra I calculated Lab=11/6 H. Anyone concur?

8. ### The Electrician AAC Fanatic!

Oct 9, 2007
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Yes, that's what I get also, but shouldn't we ask the OP to show some work before we give the answer?

9. ### t_n_k AAC Fanatic!

Mar 6, 2009
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Sure - I agree. I'm guessing the OP's teacher wouldn't be satisfied with the just the unworked answer. From my experience as a student it was always frustrating not to have the 'correct' answer. At least you had a check of your worked result. But we haven't heard from the OP anyway, so I'm also guessing they have moved on.

10. ### JoeJester AAC Fanatic!

Apr 26, 2005
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Unfortunately that happens, which is why the rules get mentioned so often.

11. ### nlr_1986 Thread Starter New Member

Aug 20, 2010
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ur answer is right but how u get it?

12. ### nlr_1986 Thread Starter New Member

Aug 20, 2010
5
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sorry for not replying in time
i was applying KVL in circuit shown in figure.and try to get equation
v=Leqdi/dt

but i get answer by that is 1.25

so plz tell me the procedure to get right answer that is 1.83H

13. ### The Electrician AAC Fanatic!

Oct 9, 2007
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Do you know how to write the loop equations for a circuit? Did you try to do this for your problem?

I'll have another look for your response in a few hours.

If you will show the details of how you got 1.25, perhaps we could you find the error in your calculations.

Last edited: Aug 30, 2010